ICOM OPC-980 adapter needed to modify/program ICOM marine radios like: IC-M302, IC-M304, IC-M402, IC-M422, IC-M422, IC-M502, IC-M504, IC-M505, IC-M602, IC-M603, IC-M604 You need an OPC-478 adapter as well to modify/program your radio with the appropriate ICOM cloning software. Pls. check your radio's service manual for the 8-pin connector, the programing pin is at pin 8 and named ICF3 .